The engine heads of internal combustion engines, and particularly of large diesel engines, are extremely complex structures which have numerous internal coolant, air, or fuel mixture passages, and also intake and exhaust valve and fuel injector ports which are required for proper combustion and containment of the hot, high pressure gases. Seals about the fuel injectors and complementing precombustion chambers may leak, and cracks may develop in the walls which separate the many internal cavities; and if this occurs a detrimental intermixing of coolant fluid, gas, fuel, antifreeze, lubricating oil and other additives can occur. Regularly scheduled spectrophotometer analysis of oil samples from such engines indicates the seriousness of leakage and when engine repairs are in order but, even when this is known, the leaks are very difficult to locate.
The engine head must be removed from the engine, the ports which connect the internal coolant cavities with the related cavities in the engine block must be plugged, and either compressed air or water under pressure must then be introduced to the coolant cavity in an attempt to locate any cracks or leaks between the coolant cavity and any of the other cavities or passages in the engine head.
Engine heads come in many different sizes and with numerous different patterns of cavities, passages and ports; so sealing all the necessary ports and openings requires a variety of plates, plugs, etc.
The problem of locating leaks and cracks is compounded by the fact that some leaks show up only when the coolant cavity is filled with water or other coolant at relatively high temperature and a pressure comparable to that at which the system operates in service. It is both difficult and dangerous to initially locate leaks and cracks by means of hot water under pressure, because a bad crack can spray scalding water around the test area. Thus, it is desirable to proceed as far as possible with compressed air, repair all leaks and cracks which are located by the use of compressed air, and then give the engine head a final test at relatively high temperature and with water under pressure.